Generally speaking, you’re free to transfer or withdraw money out of Stash whenever you want.  There are a few caveats, though:

• If you have investments, first you have to sell those and wait for the SEC-mandated holding period to be over. For more information on this, check out this article.
• Generally speaking, it can take up to 5 business days for transfers or withdrawals to show up in your external account. Keep in mind that business days are from Monday to Friday, excluding US bank holidays. If you’ve initiated a transfer on a weekend or bank holiday, the process may take slightly longer.
• Referral and promotional funds must remain in your Stash account for at least 90 calendar days before they can be transferred.
• You can only transfer your available balance in your Stash Banking account or your amount available to transfer in your Portfolio Cash. Here’s how to find these amounts in the app:
• From the Home screen, tap Transfer on the bottom navigation bar.
• Here you’ll see the available balance for your Bank account as well as the amount available to transfer in your Personal portfolio.